"Asymmetric Digital Subscriber Line" is what ADSL stands for. An example of a DSL internet link is ADSL. It transmits digital data over copper telephone lines, just like SDSL. The term "asymmetric" denotes a difference between the upload and download capacity; the customer is provided with a greater download performance than an upload speed.

Due to the restricted capacity provided by a copper telephone line, an ADSL Internet link is unequal. The frequency spectrum that is carried over the lines is divided into various portions for upload and download data, with the Provider deciding which portion of the spectrum is assigned to which. Providers assign more of that bandwidth to download rates than to transfer speeds because the majority of residential Internet users receive much more data than they send.

Contrarily, an SDSL line equally divides the range that is accessible. The highest download speed of an SDSL line is lesser than that of an ADSL line as a result, but this also creates a balanced link with identical transfer and download rates.